Abstract Young (aged 18-29) Black men who have sex with men (YBMSM) in Atlanta experience high rates of HIV acquisition (8.9%/year) and STI infection (30%/year). Over the past 5 years, we have followed a cohort of 300 YBMSM in Atlanta and have offered PrEP as part of a comprehensive package of prevention interventions. We have had substantial uptake of PrEP ? over 40% of YBMSM initiated PrEP ? but we have also observed high rates of PrEP discontinuation (39% of all PrEP starts) and ongoing high rates of new STI diagnoses. Even with 44% PrEP uptake in the cohort, HIV incidence remained high at 6.2%/year. This represents a 30% reduction in HIV incidence compared to our pre-PrEP comparison cohort, but is still unacceptably high. Therefore, we proposed to continue our cohort approach but to add three new interventions: (1) an innovative ?early warning? system to identify YBMSM on PrEP who are at risk for discontinuing PrEP, and providing a motivational interviewing-based peer intervention; (2) offering on-demand PrEP to men who decline daily PrEP or who plan to stop daily PrEP because they are unwilling to take a daily pill or perceive their risks to be infrequent; and (3) offering STI PEP with doxycycline for all men, regardless of PrEP use, to avert new STIs. This is an implementation-focused, single arm cohort approach, using a target trial design to emulate a randomized trial and evaluation of process measures. Primary outcomes are rates of PrEP discontinuation and rates of new STI diagnoses.